CN104792269B - A kind of calculation method of the fiber end face height value insensitive to linear phase-shift error - Google Patents

Abstract

The invention discloses a kind of calculation method of the fiber end face height value insensitive to linear phase-shift error, belongs to fiber end face measuring instrument technical field.Described calculation method obtains the relation of light intensity value and contrast first, is calculated the maximum position of contrast；Then phase value is constructed, is computed showing that constructed phase value is equal with actual phase, the height value for obtaining fiber end face every bit using the phase place of construction.The height value obtained using the method, eliminates linear phase-shift error for the impact of fiber end face height value；When fiber end face height value is resolved, for linearity error ε of phase-shifter is insensitive, and there is the advantages of calculating speed is fast, and precision is higher.

Description

A kind of calculation method of the fiber end face height value insensitive to linear phase-shift error

Technical field

The present invention relates to a kind of calculation method of the fiber end face height value insensitive to linear phase-shift error, belongs to optical fiber End surface measurement instrument technical field.

Background technology

Fiber end face measuring instrument is the principle based on white light interference, interferes bar using phase shift so as to realize fiber end face The change of stricture of vagina.Fiber end face tester can be with non-contacting measurement optical fiber surface pattern accurately and fast.Biography as optical signal Defeated medium, fiber end face form directly affect optical signal transmission performance in a fiber, and therefore fiber end face is measured to end face shape The measurement of state is most important in Fibre Optical Sensor and transmission.As fiber end face measuring instrument disclosure satisfy that optical fiber in production, application During on-line testing demand, therefore, it is possible to be widely used in high power laser, military opto-electronic device, fiber-optic current sensor The high-grade, precision and advanced sciemtifec and technical sphere such as device.

Fiber end face measuring instrument during interferometry, changed by phase-shifter reference beam and test beams it Between optical path difference, while some width interferograms of collection, then carry out solving the height for obtaining fiber end face to interferogram.To dry When relating to figure and being solved, it is desirable to which phase-shift phase is very accurate, and therefore phase displacement error is very big for the measuring and calculating of fiber end face height has Affect, therefore design a kind of height value measuring method insensitive to linear phase-shift error particularly important.

Content of the invention

The invention aims to solving the above problems, a kind of measurement optical fiber insensitive to linear phase-shift error is proposed The height value calculation method of end face three-dimensional appearance, can be used for the shadow for ignoring linear phase-shift error in fiber end face measuring system Ring.

Described calculation method specifically includes following steps：

The first step, obtains the relation of light intensity value and contrast；

Second step, is calculated the maximum position of contrast；

3rd step, constructs phase value, obtains height value；

Present invention advantage compared with prior art：

When fiber end face height value is resolved, for the linearity error of phase-shifter is insensitive, and have calculating speed fast, The advantages of precision is higher.

Description of the drawings

Fig. 1 is fiber end face measuring system schematic diagram；

Fig. 2 is the graph of a relation of white light interference light intensity and optical path difference.

Specific embodiment

The present invention is described in detail with reference to the accompanying drawings and examples.

As shown in Fig. 1 the principle schematic of fiber end face measuring system, the reflected mirror folding of the light that white light source sends Turn, reach Amici prism, incide on microcobjective through Amici prism, converged light, a portion light are produced by microcobjective Converge on fiber end face, another part light is by Amici prism reflecting focal to index plane.Anti- by index plane and fiber end face The two light beam convergences that penetrates, form interference fringe, project on the target surface of CCD through microcobjective, a cube Amici prism.Piezoelectricity is made pottery When porcelain (PZT) phase-shifter drives index plane to move, interference fringe can change.

Fiber end face measuring instrument measures three-dimensional appearance, is the light intensity value according to the interference fringe image for being gathered, obtains thing The relative altitude value in body surface face, its it is critical only that the position at the maximum relevant peak of the position i.e. light intensity value for accurately finding zero optical path difference Put.White light interference light intensity has relation as shown in Figure 2 with optical path difference, and when optical path difference is 0, light intensity reaches maximum.

Based on above-mentioned fiber end face measuring system, and the relation of optical path difference and light intensity, the resolving side that the present invention is provided Method realizes that step is as follows：

(1) relation of light intensity value and contrast is obtained；

The present invention carries out the high computational of fiber end face using round-about way, allows the maximum of intetference-fit strengthening γ As the condition of light intensity peak value, order：

Wherein γ be intetference-fit strengthening, I_maxFor the maximum of light intensity, I_minFor light intensity minima.

Due to the two-beam vibrations synthesis formula reflected by index plane and fiber end face：

Wherein I_aRepresent the light intensity value of the light reflected by fiber end face, I_bRepresent the light intensity value of the light reflected by index plane, I The intensity level of the light of synthesis is represented,The position difference of two-beam is represented, so

I.e.

Make I₀=I_a+I_bCan then obtain：

When fringe contrast γ reaches maximum, the intensity level I of light is peak value.

(2) the maximum position of contrast is calculated；

In measurement process, it is accurately linear mobile that piezoelectric ceramics drives index plane to carry out, and the step-length of piezoelectric ceramics is selected For λ/8, centre wavelengths of the λ for white light source, then the relative phase shift amount of adjacent pattern is theoretically pi/2, but piezoelectric ceramics meeting There is a linear phase displacement error, be designated as ε, then phase-shift phase is reformed intoPiezoelectric ceramics often moves a step-length, CCD will gather a frame interference image, use I₁～I₅To represent the light intensity value of certain point in continuous five two field picture, using these Light intensity value is being calculated, and obtains contrast γ.

After arrangement it is：

As available from the above equation：

So as to obtain：

γ²∝(2I₃-I₁-I₅)²+(I₄-I₂)²

When γ obtains maximum, phase shift times N now is recorded；

(3) phase value is constructed, obtains height value；

One phase value of constructionOrder

Can obtain：

Above formula is further spread out, as ε is very little value, approximate cos (i* ε) ≈ 1, sin (i* ε) ≈ i* can be made ε, obtains：

Wherein, i is 0,1,2,3,4.

The phase value for being constructedWith actual phase valueValue be equal, it is possible to calculated with following formula Height value h：

Wherein,

Claims (1)

1. a kind of calculation method of the fiber end face height value insensitive to linear phase-shift error, it is characterised in that described solution Calculation method specifically includes following steps：

The first step, obtains the relation of light intensity value and contrast；

Light intensity value with the relation of contrast is：

$\mathrm{\γ}=\frac{I_{\max }-I_{\min }}{I_{\max }+I_{\min }}$

Wherein γ be intetference-fit strengthening, I_maxFor the maximum of light intensity, I_minFor light intensity minima；

The two-beam vibrations synthesis formula reflected by index plane and fiber end face：

Wherein I_aRepresent the light intensity value of the light reflected by fiber end face, I_bRepresent that the light intensity value of the light reflected by index plane, I are represented The intensity level of the light of synthesis,The position difference of two-beam is represented, so,

$I_{max}=I_a+I_b+2\sqrt{I_a{I}_b}$

$I_{min}=I_a+I_b-2\sqrt{I_a{I}_b}$

That is,

Make I₀=I_a+I_bThen obtain：

When fringe contrast γ reaches maximum, the intensity level I of light is peak value；

Second step, is calculated the maximum position of contrast；

The linear phase displacement error of piezoelectric ceramics is designated as ε,The position difference of two-beam is represented, λ is the centre wavelength of white light source, Use I₁～I₅To represent the light intensity value of certain point in continuous five two field picture, calculated using these light intensity values, and obtain right Than degree γ；

After arrangement it is：

Obtained by above formula：

So as to obtain：

γ²∝(2I₃-I₁-I₅)²+(I₄-I₂)²；

3rd step, constructs phase valueHeight value is obtained, specially：

One phase value of constructionOrder

Arrangement is obtained：

Above formula is further spread out, as ε is very little value, is made approximate cos (i* ε) ≈ 1, sin (i* ε) ≈ i* ε, is obtained：

The phase value of constructionWith actual phase valueValue be equal, so with following formula computed altitude value h：

Wherein, phase shift number of times when N is intetference-fit strengthening γ maximums,